Performance improvement by discharge from different levels in solar storage tanks

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.01.005 Byline: Simon Furbo, Elsa Andersen, Alexander Thur, Louise Jivan Shah, Karin Dyhr Andersen Keywords: SDHW systems; Solar combisystems; Heat storage tanks; Thermal stratification; Advanced discharge strategies Abstract: The thermal advantages by utilizing discharge from different levels in solar storage tanks are investigated, both for a small SDHW system and for a solar combisystem. The investigations showed that it is possible to increase the thermal performance of both types of systems by using two draw-off levels from the solar tanks instead of one draw-off level at a fixed position. The best position of the second draw-off level is in the middle or just above the middle of the tank. For the investigated small SDHW system with a realistic draw off hot water temperature of 40[degrees]C and 45[degrees]C and an auxiliary volume temperature of 50.5[degrees]C the increase of the thermal performance by the second draw-off level is about 6%. For the investigated solar combisystem the increase in thermal performance by using one extra draw-off level, either for the domestic hot water heat exchanger or for the heating system, is about 3%, while an improvement of about 5% is possible by using a second draw-off level both for the domestic hot water heat exchanger and for the heating system. Author Affiliation: Department of Civil Engineering, Technical University of Denmark, Building 118, DK-2800 Kgs. Lyngby, Denmark Article History: Received 13 July 2004; Revised 12 January 2005; Accepted 13 January 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Erich Hahne